Interpolymerization of ethylene



atented 8y 1 I 1 'rron 2,206,429 mam orrlcs Michael Wilicox Perrin, Eric William Fawcett. John Greves Paton, and Edmond George Williams, Northwich, England, assignors to Imperial Chemical Industries Limited, "acor notation of Great Britain a f 1 No Drawing. Application April 21, 1938, Serial N0. 203,442. In Great Britain All! 22, 193'! I 19 Claims.

A still further object is to devise methods of a manufacturing new organic compounds of high molecular weight. Further objects will appear hereinafter. These objects are accomplished by the following invention.

We have found that if we subject ethylene together with other polymerizable organic compounds containing one or more double bonds to conditions of pressure and temperature similar to those required for the conversion of ethylene into solid or semi-solid polymers, we obtain valuable high-molecular interpolymerization products, i. e. compounds of high molecular weight relative to any of the starting materials, by the polymerization of one or more of the starting materials and the occurrence of chemical reaction or reactions between the different kinds of molecules'present at some stage of the polymerization. The reaction conditions for the conversion of ethylene, which may contain a small amount of oxygen, are disclosed in pending U. S. application Serial Nos. 123,722 filed Feb. 2, 1937 and 157,810 filed Aug. 6, 1937 and comprise the use of pressures of at least 500 atmospheres, e. g. 1500 atmospheres or more, and temperatures between 100 and 400 C. Such pressure and temperature conditions apply also to the present invention and a small quantity of oxygen, for example between 0.01 and per cent, may advantageously be present.

The invention is illustrated but not limited by the following examples.

Example 1 A sealed glass tube containing cc. of liquid butadiene is placed in a thick-walled steel pressure vessel ,of 80 c. c. capacity. The vessel is filled with ethylene containing 0.1% by weight of oxygen, to a pressure of 1,500 atmospheres, so that the glass tube is broken. The contents of the vessel are stirred mechanically and it is heated at 230 C. for 3 hours, the pressure being adjusted to 1500 atmospheres in the hot. The product-consists of 16 grams of a very viscous liquid, which dries on exposure to air to give a soft rubbery solid. By treatment of the liquid product at 100 C. in a. good vacuum some butadiene dimer is removed'by distillation, and by extraction with hot benzene some solid polymen of ethylene is removed. The residue, about by weight ofthe originalproduct, is sparingly soluble in hot benzene and is an interpolymer of ethylene and butadiene, as shown by the presence in it of a number of double bonds.

Example 2 A This example shows the formation of interpolymers-of ethylene and styrene in various proportions. I

In three experiments, quantities of c. c., 10 c. c., and 5 c. c. respectively of styrene monomer are added to a thick-walled steel reaction vessel of 80 c. c. capacity. Ethylene containing 0.04%

by-weight of oxygen is compressed into-the vessel to a pressure of 1500 atmospheres. The contents of the vessel are stirred mechanically andit is heated at 200 C. for 20 hours in each case the pressure being adjusted to 1500 atmospheres in the hot. An interpoiymer of styrene and ethylene is formed in each case. By analysis of the carhon-hydrogen ratio, in the first experiment the interpolymer is found to contain 15% by weight of styrene; in the second 53%, and in the third 40%. The product of the first experiment is a hard tough solid; that of the second experiment is a hard pliable solid; and that of the third experiment is a tough rubbery solid.

The molecular weight of the interpolymer is, in each case, about 10000. That the products are true interpolymers may be seen from the fact that they are homogeneous, while polymerized ethylene and polymerized styrene are not compatible with each other.

Example 3 A mixture of 83 per cent by weight of ethylene containing 0.06% of oxygen and 17 per cent by weight of stilbene is subjected to a temperature of 210 C. at a reaction pressure of 2500 atmospheres for several hours. The reaction product is a dark solid of molecular weight about 3000. It softens at 85 C.

Under the same conditions a reaction mixture consisting of equal parts by weight of ethylene and stilbene gives a product which has a molecuiar weight of over 3000 and a softening point of91 C. 'I'hisproduct can be worked up into the form of films by the usual methods.

Example 4 Example 5 A quantity of 10 c. c. of maleic acid diethyl ester is piacedin a thick-walled steel reaction 0.06 per cent of oxygen is compressed into the vessel to a pressure giving a reaction pressure of vessel of 80 c. c. capacity. Ethylene containing 1500 atmospheres. The contents of the vessel are stirred mechanically and it is heated at 210' C. for 17 hours.

The reaction product contains about 30 per cent of ester in the form of an interpolymer with the polymerized ethylene. The softening point of the product is 94 C.

Example 6 The procedure of Example 5 is repeated using 10 c. c. of the diethyl ester of fumaric acid instead of the diethyl ester of malelc acid.

The reaction product contains about 25 per,

cent of the ester and has a softening point of C. 1 Example 7 The procedure of Example 5 is repeated using 10 c. c. of the dlethyl ester of itaconic acid instead of the diethyl ester of maleic acid.

The reaction product contains about 25 per cent of the ester and has a softening point of 97 C.

Example 8 is about 1.1 ken/mm, that of the 80% product is about 3.7; the softening points are respectively about 108 C. and C. It appears that both the tensile strength and softening point first pass through a minimum with increasing methyl methacrylate content, before assuming the higher values quoted.

The products can be cold-drawn, with a substantial increase in their tensile strength. They can be readily compression-moulded.

Example 10 A quantity of 10 c. c. of butyl methacrylate is placed in an autoclave of 80 c. 0. capacity and ethylene containing 0.05% of oxygen is forced in at a pressure of 1500 atmospheres. The autoclave is heated at 210 C. for 17 hours, during which time the contents are stirred mechanically.

The reaction product contains 25% of butyl methacrylate and is a soft non-elastic mass having a softening point of 99 C.

Example 11 A quantity of 1 c. c.'of glycol dimethacrylate is placed in an autoclave of 80 c. 0. capacity and ethylene containing 0.05% of omen is forced in at a pressure of 1500 atmospheres. The autoclave is heated to 210 C. for 17 hours, during which time the contents are stirred m The reaction product contains 5% oi glycol dimethacrylate .and is a sparingly soluble solid having a high scratch hardness.

Example 12 A quantity of 10 c. c. of vinyl acetate is placed in an autoclave of 80 c. 0. capacity and ethylene containing 0.06% of oxygen is forced in at a pressure of 2500 atmospheres. The autoclave is heated to 210 C. for 18 hours, during which time the contents are stirred mechanically.

The reaction product is a solid of softening point 92 C. which can readily be drawn into threads. It contains about 25 per cent of vinyl acetate in the form of an interpolymer with the polymerized ethylene.

Example 14 A mixture containing-40 per cent by weight of ethylene and 60 per cent by weight of isobutylene, together ,with an amount of benzoyl peroxide equivalent to 0.1 per cent by weight of the mixture of available oxygen, is subjected to a temperature of 210 C. and a pressure of 1500 atmospheres for about 17 hours. The reaction product is a mixture of a soft solid and a liquid of terpene-like character.

Example 15 A mixture containing 80 er cent by weight of ethylene and 20 per cent by weight of amylene is subjected to a temperature of 250 C. and a pressure of 2500 atmospheres for 3 hours. The reaction product is a hard wax resembling paraiiln wax, having a molecular weight between 1500 and 2000.

The pressures given in the above examples are the pressures at which the reaction is actually carried out, that is to say, either we start with a lower initial pressure which goes up to the required pressure on heating or we start at about the reaction pressure and keep it controlled throughout the heating.

Interpolymerization appears, in general, to lead to the production of one or other types of products:

(a) Mixed single chain polymers, i. e. polymers having a long chain structure in which, in the normal chain of CH: groups characteristic of ethylene polymers, other groups are inter at various points or intervals.

(b) Cross-linked or branched chain compounds in which single chains of the ethylene polymer type or of the mixed single chain type just mentioned, are linked or branched together directly or via intermediate groupings. In either case, the resulting products have characteristics differing from those of ethylene polymers to an extent depending upon the nature of the starting materials and the degree of interpolymerization. In cross-linkage polymeristion, the general eilect is to increase the melting point and decrease the solubility of the polymer. Similar or converse effects can be obtained in interpolymerization of the first, i. e. the mixed single chain type.

As starting materials, in addition to ethylene, may be mentioned monovinyl unsaturated hydrocarbons, e. g. ropylene, isobutylene, amylene. styrene and stilbene; esters of unsaturated polybasic acids, e. g. the diethyl esters of maieic,

of the following fumaric, citraconic and itaconic acids or the triethyl ester of aconitic acid; the esters of acids of the acrylic and substituted acrylic series, e. g. methyl, butyl and glycol methacrylates; vinyl esters, e. g. vinyl acetate and chloride; and comzoyl peroxide. Inert gaseous diluents, e. g. nitrogen, may also be present.

As will be appreciated from the foregoing description and examples, a wide range of interpolymerization products of ethylene with various organic compounds can be prepared under the conditions of this invention. Thus, the products may range from soft to tough or very hard solids, some rubbery, some wax-like. The significant point is, that the invention provides a method for obtaining products having properties which are different from those of the solid polymers obtained from ethylene alone. The character of the product can be varied greatly by choice of interpolymerizing compound, reaction conditions (temperature, pressure and duration), proportions of reactants, etc.

Some of the products are capable of being extruded or otherwise formed into films, threads, tubes, rods, sheets, tapes, ribbons and similar shaped forms, e. g. the interpolymers of ethylene and vinyl esters, styrene and esters of dibasic unsaturated acids, acrylic and substituted acrylic acid esters. Such films, etc., can be used for waterproofing purposes, electrical insulation, protection from corrosion and chemical attack, etc. The wax-like products may be employed for all purposes for which existing waxes are employed, e. g. polishes. Certain of the products, e. g. the interpolymers of ethylene with esters of dibasic unsaturated acids and vinyl esters can readily be obtained in the form of aqueous emulsions by standard emulsification technique. Their emulsiiying properties are increased if they are first subjected to partial hydrolysis, e. g. by heating an aqueous suspension or emulsion with acid or preferably alkali. The interpolymers containing higher percentages of esters of dibesic unsaturated acids, when partially hydrolyzed, have surface active properties and may be used as emulsifying agents.

, As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. A method of manufacturing organic compounds of high molecular weight which comprises heating to a temperature of between C. and

, 4. A method as claimed in claim 1, in which the other polymerizable organic compound is selected from the group consisting of polymerizable monovinyl and divinyl hydrocarbons. 5. A method as claimed in claim 1, in which the other polymerizable organic compound is selected from the group consisting of polymerizable monovinyl and divinyl esters.

6. A method as claimed in claim 1, in which the other polymerizable organic compound is selected from the group consisting of polymerizable esters of unsaturated monoand polybasic acids.

7. A method as claimed in claim 1, in which the other polymerizable organic compound is methyl methacrylate.

8. A method as claimed in claim 1, in which the other polymerizable organic compound is styrene.

9. An interpolymer of ethylene and at least one other polymerizable organic compound having ethylenic unsaturation, said interpolymer being that obtained by heating a mixture of ethylene and said compound at a temperature of 100 C. to 400 C. under a pressure of more than 500 atmospheres.

10. The interpolymer set forth in claim 9 in which said polymerizable organic compound is selected from the group consisting of polymerizable monovinyl and divinyl hydrocarbons.

11. The interpolymer set forth in claim 9 in which said polymerizable organic compound is selected from the group consisting of polymerizable monovinyl and divinyl esters.

12. The interpolymer set forth in claim 9 in which said polymerizable organic compoimd is selected from the group consisting of polymer- Z331: esters of unsaturated monoand polybasic 13. An interpolymer of ethylene and at least one other polymerizable organic compound having ethylenic unsaturation, said interpolymer being that obtained by heating a mixture of ethylene and said compound at a temperature of 100 C. to 400 C. under a pressure of at least 1500 atmospheres.

14. The interpolymer set forth in claim 9 in which. said polymerizable organic compolmd is an adesterd of an alpha-methylene monocarboxylic 15. The interpolymer set forth in claim 9 in.

which said polymerizable organic compound is an aliphatic monohydric alcohol ester of an alphamethylene monocarboxylic acid.

18. The interpolymer set forth in claim 9 in which said polymerizable organic compoimd is an acyclic monohydric alcohol ester of an alphaalkyl substituted acrylic acid.

1'). The interpolymer set forth in claim 9 in which said polymerizable organic compound is methyl methacrylate.

18. The interpolymer set forth in claim 9 in which said polymerizable organic compoimd is 400 C. at a pressure of more than 500 atmosstyren 'pheres a mixture containing ethylene and at least one other polymerizable organic compound having ethylenic unsaturation.

2. Amethodasclaimedinclaim Linwhichthe used is at least 1900 atmospheres. 3.Amethodasclaimedinclaiml.inwhich thereispresentasubstancc cftheclassconsisting of men and oaldhng agents.

19. The interpolymer set forth in claim 9 in which said polymerizable organic compoimd vinyl acetate.

MICHAEL WILLCOX PERRIN. RIC WILLIAM FA WCEII. JOHN G. PATON. mom: G. WILLIAM 

